The present invention relates to an articulated robotic manipulator having a plurality of segments between a fixed base and its distal end. It is more particularly concerned with an electrically operated direct drive manipulator.
Electrically powered manipulators presently in use for robots are considered inferior to human arms and are unsatisfactory for many applications, both with respect to speed of operation, accuracy and versatility. A principal reason for their poor performance is found in the transmission mechanisms such as gear trains, lead screws, belts, chains and linkages which are used to transmit power from the drive motors to the load and to increase the drive torque. These transmission mechanisms are subject to friction and backlash and require careful adjustment and regular maintenance.
With one type of robotic manipulator heretofore known, each of the joints between segments includes a member positioned closer to the fixed base, which member may be called a driving member, provided with an electric motor with a gear mounted on the output shaft of the motor, and a driven member positioned closer to the distal end of the arm and provided with a gear of larger diameter than the gear. The driven member is operated by the motor through the gears for speed reduction. Since each of the joints between the segments is thus provided with a motor and reduction gear mechanism, the manipulator is undesirably bulky and heavy.
Other manipulators are also known in which each joint between segments includes a hydraulic cylinder connecting a segment or member positioned closer to the fixed base to a driven member. Such manipulators, however, are also bulky and heavy, while oil leaks and other troubles are likely to result in reduced control accuracy.